Multi-type heat-sensitive transferring medium

ABSTRACT

A multi-type heat-sensitive transferring medium comprises a substrate and a heat-sensitive transferring ink layer overlying the substrate and comprising a resin component, a solid component immiscible with the resin component and capable of becoming liquid by heating while solid at room temperature, and a coloring agent, the resin component being (a) a vinyl chloride-vinyl acetate copolymer having a monomer weight ratio of vinyl chloride to vinyl acetate of from 65:35 to 90:10 and having a viscosity average degree of polymerization of 200-1000, or (b) a polymethacrylic acid ester having a viscosity average degree of polymerization of 100-3000, or (c) a mixture of (a) and (b).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a heat-sensitive transferring medium capableof being used many times (hereinafter referred to as "multi-typeheat-sensitive transferring medium").

2. Description of the Prior Art

Heretofore, multi-type heat-sensitive transferring media have beenknown. For example, Japanese Patent Application Laid-open No.105579/1980 discloses a heat-sensitive transferring medium comprising abase film and a layer of a porous and network structure having finepores containing a heat melting ink which can be used repeatedly manytimes, and Japanese Patent Application Laid-open Nos. 89984/1981 and36698/1982 and others disclose heat-sensitive transferring mediacomprising a base film and an ink layer overlying the base film andcomposed of dye, binder, low melting agent and fine powders, and the inklayer being consumed subsequently from the surface layer and the mediabeing able to be used many times.

However, they are of low sensitivity and cause much smear.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a multi-typeheat-sensitive transferring medium free from the above-mentioneddrawbacks.

Another object of the present invention is to provide a multi-typeheat-sensitive transferring medium having a high sensitivity, free fromsmearing, and of an excellent durability.

According to the present invention, there is provided a multi-typeheat-sensitive transferring medium which comprises a substrate and aheat-sensitive transferring ink layer overlying the substrate andcomprising a resin component, a solid component immisicible with theresin component and capable of becoming liquid by heating while solid atroom temperature, and a coloring agent, the resin component being (a) avinyl chloride-vinyl acetate copolymer having a monomer weight ratio ofvinyl chloride to vinyl acetate of from 65:35 to 90:10 and having aviscosity average degree of polymerization of 200-1000, or (b) apolymethacrylic acid ester having a viscosity average degree ofpolymerization of 100-3000, or (c) a mixture of (a) and (b).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The vinyl chloride-vinyl acetate copolymer has a monomer weight ratio ofvinyl chloride to vinyl acetate ranging from 65:35 to 90:10, preferably,from 70:30 to 80:20 and a viscosity average degree of polymerization of200-1000. The polymetharylic acid ester has a viscosity average degreeof polymerization of 100-3000.

Outside of the above-mentioned numerical ranges, the multi-typeheat-sensitive transferring medium has poor characteristics that is, lowsensitivity, smearing and low durability.

As the polymethacrylic acid esters, there may be used the lower alkylester such as methyl ester, ethyl ester, propyl ester, butyl ester andthe like.

Though it is not desired that the present invention is restricted by anymechanism, the vinyl chloride-vinyl acetate copolymers, thepolymethacrylic acid esters as specified, or a mixture thereof seems togive the good results due to a good dispersability of the resincomponent and the heat-sensitive transferring ink, and theheat-sensitive transferring ink filling a number of continuous pores.

As the solid component immiscible with the resin component and capableof becoming liquid by heating while solid at room temperature, there maybe used paraffin wax, microcrystalline wax, ceresine wax, montan wax,carunauba wax, polyethylene wax, polyethylene oxide wax, caster wax,tallow hardened oil, carbowax, Japan wax, lanorin, stearic acid, stearicacid monoglyceride, sorbitan stearate, sorbitol hexastearate,pentaerthrytol stearate, polyoxyethylene monostearate, stearyl alcohol,other synthetic oxide waxes, synthetic or natural ester waxes,hydrogenated waxes and the like, and stearic acid, stearic acidmonoglyceride, and sorbitan stearate are preferable.

The weight ratio of the resin component to the solid componentimmiscible with the resin component and capable of becoming liquid byheating while solid at room temperature is preferably from 2:1 to 1:2.

As the coloring agents, there may be used conventional dyes, pigments,and other color-forming materials and materials capable of recording,such as alkaline basic dye, neozapon dye, Zapon dye, carbon black, Lakered, alkali blue, prussian blue, crystal violet lactone, magnetic ironoxide and the like.

As a volatile solvent for forming the heat-sensitive transferring ink,there may be used organic solvent such as toluene, ethyl acetate, methylethyl ketone, methanol and the like and water and the like. Thesesolvents are selected such that the solvent can be a solvent for theresin component and can be a solvent or dispersion medium for the solidcomponent. The solvents may be used alone or in combination.

The multi-type heat-sensitive transferring medium may be produced bypreparing an ink coating material composed of the resin component, thesolid component and a coloring agent dissolved and/or dispersed in avolatile solvent, applying the ink coating material to a substrate suchas paper, resin film, metal sheet and the like according to aconventional method, and drying to form a heat-sensitive transferringlayer adhered to the substrate.

If desired, in order to enhance the adhesion between the heat-sensitivetransferring layer and the substrate, there may be formed preliminarily,on the substrate, an undercoating bonding layer composed of a resin suchas polyester, vinyl chloride-vinyl acetate copolymer, acrylic resins,vinyl chloride resins and the like, or a plasticizer.

The viscosity average degree of polymerization of the vinylchloride-vinyl acetate copolymer is measured according to JIS K6721-1977, para. 3.1 , 3. (P: mean polymerization degree). That of thepolymethacrylic acid ester is measured according to the formula,P=[η]-0.0095/0.47×10⁻⁴, where η is a limiting viscosity number, IchiroSakurada: KOBUNSHI KAGAKU, Vol. 2, pp. 253-260 (1945).

The present invention, will be further explained by referring to thefollowing examples.

EXAMPLE 1

    ______________________________________                                        Vinyl chloride-vinyl acetate copolymer                                                              10     parts by weight                                  (Viscosity average degree of                                                  polymerization: about 400)                                                    Stearic acid          13     parts by weight                                  Nigrosine             3      parts by weight                                  Carbon black          3      parts by weight                                  toluene               26     parts by weight                                  Ethyl acetate         45     parts by weight                                  Total                 100    parts by weight                                  ______________________________________                                    

Stearic acid, nigrosine, and carbon black were mixed at 80° C. anddispersed in a solution of vinyl chloride-vinyl acetate copolymer intoluene and ethyl acetate. The resulting coating material was applied toa polyester film of 3 microns thick subjected to a sticK-preventingtreatment (forming a stick-preventing layer of about 0.2 g/m² byapplying a 3% aqueous solution of a mixture of potassiumdi(polyoxyethylene) lauryl ether phosphate and dipotassium mono(polyoxyethylene) lauryl ether phosphate) to produce a heat-sensitivetransferring layer. The coating material was applied to the surface ofthe polyester film to which the stick-preventing treatment had not beenapplied.

The multi-type heat-sensitive transferring medium was tested by printingat the same portion 30 times using P6 printer (tradename, manufacturedby Fuji Xerox Co.).

The test was carried out by changing variously the weight ratio of vinylchloride to vinyl acetate. The results of Examples 1-1 to 1-8 are shownin the following Table 1.

                  TABLE 1                                                         ______________________________________                                        Vinylchloride-vinyl                                                           acetate copolymer                                                             Vinyl    Vinyl    Sensitivity*.sup.1                                              chloride acetate  Den-  Reso-          Dura-                                  (%)      (%)      sity*.sup.2                                                                         lution*.sup.3                                                                        Smearing*.sup.4                                                                       bility*.sup.5                      ______________________________________                                        1-1 100       0       0.71  Δ                                                                              0.31    X                                  1-2 95        5       0.82  ○                                                                             0.17    Δ                            1-3 90       10       0.98  ○                                                                             0.15    ○                           1-4 80       20       1.15  ⊚                                                                     0.12    ⊚                   1-5 70       30       1.13  ⊚                                                                     0.11    ⊚                   1-6 65       35       0.99  ○                                                                             0.17    ○                           1-7 60       40       0.81  ○                                                                             0.29    Δ                            1-8 50       50       0.69  Δ                                                                              0.27    X                                  ______________________________________                                        *.sup.1 Sensitivity is defined as a state of the                              resulting printing at a low energy, that is, when the heat                    generated by the thermal head is small. When the state                        of the resulting printing is good, the sensitivity is                         regarded as good. The state of the resulting printing is                      evaluated on the basis of both density and resolution of                      the printed image. When the printed image is excellent in                     both density and resolution, said state of the resulting                      printing is regarded as excellent.                                            *.sup.2 Density is determined by using MACBETH RD-514                         densitometer (tradename, manufactured by Koll Morgen Co.)                     (averaged value of 30 measurements).                                          *.sup.3 Resultion is evaluated by eye-observation and                         classified into four degrees, from excellent to poor, by                      the following signs: ⊚,  ○ , Δ, X. -*.sup.4       Smearing is determined by measuring the smearing                              around the printed image produced by reciprocating                            rubbing for 3 minutes at a speed of 43 times per minute                       under a load of 908 g (2 lb.) by means of Rub Tester                          produced by YASUDA SEIKI SEISAKUSHO K.K.                                      *.sup.5 Printed image density of the first printing is                        compared with that of the 30th printing. The following                        four degrees are used to show the result:                                     Density change ⊚                                               within 10% of density of                                                      the first printing                                                            Density change within                                                                        ○                                                       20% of density of the                                                         first printing                                                                Density change within                                                                        Δ                                                        30% of density of the                                                         first printing                                                                Density change over                                                                          X                                                              30% of density of the                                                         first printing                                                            

As is clear from Table 1 above, where the weight ratio of vinyl chlorideto vinyl acetate of the vinyl chloride-vinyl acetate copolymer is withinthe range of from 65:35 to 90:10, good results are obtained. Where theweight ratio is from 70:30 to 80:20, particularly good results areobtained.

Table 2 below shows the results of the procedure similar to theabove-mentioned one except that the viscosity average degree ofpolymerization was varied (the weight ratio of vinyl chloride and vinylacetate being 75:25).

                  TABLE 2                                                         ______________________________________                                        Viscosity average                                                             degree of polymeri-                                                           zation of vinyl Sensitivity*.sup.1                                            chloride-vinyl acetate                                                                        Den-    Reso-    Smear-                                                                              Dura-                                  copolymer       sity*.sup.2                                                                           lution*.sup.3                                                                          ing*.sup.4                                                                          bility*.sup.5                          ______________________________________                                        1-9  100            0.92    Δ                                                                              0.19  Δ                              1-10 200            1.14    ⊚                                                                     0.11  ⊚                     1-11 400            1.15    ⊚                                                                     0.12  ⊚                     1-12 1000           1.18    ⊚                                                                     0.13  ⊚                     1-13 1500           0.80    Δ                                                                              0.18  Δ                              1-14 2000           0.76    Δ                                                                              0.17  Δ                              ______________________________________                                         *.sup.1 -*.sup.5 are the same as those as mentioned above.               

As is clear from Table 2 above, where the viscosity average degree ofpolymerization of the vinyl chloride-vinyl acetate copolymer ranges from200 to 1000, there is obtained a good result.

EXAMPLE 2

    ______________________________________                                        Poly (ethyl methacrylate)                                                                         8      parts by weight                                    Sorbitan stearate   16     parts by weight                                    Carbon black        5      parts by weight                                    Toluene             25     parts by weight                                    Ethyl acetate       46     parts by weight                                    Total               100    parts by weight                                    ______________________________________                                    

Sorbitan stearate and carbon black were mixed and dispersed in asolution of poly (ethyl methacrylate) in toluene and ethyl acetate, andthe resulting mixture was used to form a heat-sensitive transferringlayer following the procedures in Example 1. The resulting multi-typeheat-sensitive transferring medium was tested by printing at the sameportion 30 times by using P6 printer (tradename, manufactured by FujiXerox Co.).

Viscosity average degree of polymerization of poly (ethyl methacrylate)was changed variously to carry out the procedures of Example 2-1 toExample 2-6. The results are shown in Table 3 below.

                  TABLE 3                                                         ______________________________________                                        Viscoity average                                                              degree of polymer-                                                                          Sensitivity*.sup.1                                              zation of poly lethyl                                                                       Den-    Reso-            Dura-                                  methacrylate) sity*.sup.2                                                                           lution*.sup.3                                                                          Smearing*.sup.4                                                                       bility*.sup.5                          ______________________________________                                        2-1 50            0.89    Δ                                                                              0.18    Δ                              2-2 100           1.12    ⊚                                                                     0.12    ⊚                     2-3 2000          1.15    ⊚                                                                     0.13    ⊚                     2-4 3000          1.14    ⊚                                                                     0.12    ⊚                     2-5 3500          0.98    ○                                                                             0.15    ○                             2-6 5000          0.72    Δ                                                                              0.17    Δ                              ______________________________________                                         *.sup.1 -*.sup.5 are as defined in Table 1.                              

As is clear from Table 3, when the viscosity average degree ofpolymerization of the polymethacrylate is within the range of 100-3000,there is obtained a good result.

EXAMPLE 3

    ______________________________________                                        Vinyl chloride-vinyl                                                                              10     parts by weight                                    acetate copolymer                                                             (weight ratio of vinyl                                                        chloride to vinyl acetate,                                                    80:20; viscosity average degree                                               of polymerization, 500)                                                       Poly (methyl methacrylate)                                                                        6      parts by weight                                    (Viscosity average degree of                                                  polymerization: 2000)                                                         Stearic acid monoglyceride                                                                        8      parts by weight                                    Neozapon Firely Red 1      parts by weight                                    Lake red            4      parts by weight                                    Toluene             26     parts by weight                                    Ethyl acetate       45     parts by weight                                    Total               100    parts by weight                                    ______________________________________                                    

Repeating the procedure of Example 1 by using the above-mentionedingredients, there was produced a multi-type heat-sensitive transferringmedium. When the same portion of the medium was used 30 times to print,the 30th printed image had the same density as that of the initialprinted image and was sharp and little smearing.

EXAMPLE 4

To the surface of a polyester film of 3 microns thick where astick-preventing treatment was not effected, as used in Example 1, wasapplied a solution produced by adding 6 parts by weight of a plasticizer(DOP) to a solution of 30 parts by weight of a vinyl chloride-vinylacetate copolymer in 20 parts by weight of toluene and 44 parts byweight of ethyl acetate, followed by drying to form an undercoatingbonding layer of 2 microns thick. A coating material as used in Example3 was applied to the undercoating bonding layer to form a heat-sensitivetransferring layer.

The resulting multi-type heat-sensitive transferring medium was testedin a way similar to Example 1. The test revealed that the durability washigher than that of Example 3.

What is claimed is:
 1. A multi-type heat-sensitive transferring mediumwhich comprises a substrate and a heat-sensitive transferring ink layeroverlying the substrate and comprising a resin component, a solidcomponent immiscible with the resin component and capable of becomingliquid by heating while solid at room temperature, and a coloring agent,the resin component being (a) a vinyl chloride-vinyl acetate copolymerhaving a monomer weight ratio of vinyl chloride to vinyl acetate of from65:35 to 90:10 and having a viscosity average degree of polymerizationof 200-1000, or (b) a polymethacrylic acid ester having a viscosityaverage degree of polymerization of 100-3000, or (c) a mixture of (a)and (b).
 2. A multi-type heat-sensitive transferring medium according toclaim 1 in which the weight ratio of the resin component to the solidcomponent immiscible with the resin component and capable of becomingliquid by heating while solid at room temperature ranges from 2:1 to1:2.
 3. A multi-type heat-sensitive transferring medium according toclaim 1 in which the substrate has an undercoating bonding layer.
 4. Amulti-type heat-sensitive transferring medium according to claim 1 inwhich the monomer weight ratio of vinyl chloride to vinyl acetate rangesfrom 70:30 to 80:20.